I have a 94 XJ 4.0 and my coolant temps stay between 170 and 180!

A few months back I replaced the thermostat and thermostat housing. Coolant is clean and full and i have checked several times to make sure there is no air in the system.

Originally I thought it was a bunk thermostat so I replaced it with another Stant thermo and the same thing.

Forgot to mention that prior to changing the thermostat and housing it ran right about 209-210. Any ideas or suggestions would be greatly appreciated as my MPGs are suffering.

 

I had the same exact problem as you i went through 4 thermostats till i realized let me try a different BRAND thermostat and it worked although for some reason the old one was good it never let it warm up try going with a different brand i tried autozone duralast and it worked

 

That's really odd but for a couple bucks it couldn't hurt to try! I despise Autozone parts but if it worked for you I'll give that one a go first. Thank you much for the fast response!

 

No problem it sucked not having heat in winter and running to rich all the time

 

The really weird thing is I still put out heat like a mother f*****. I still need ti get my hands on an IR thermometer so I can see what my temp really is.

 

yeah try that because if its running at norm operate temp it could be temp sensor especially if your heater works right

 

I was thinking the same thing ...I have a couple other temp sensors laying around that I could throw in too. But my gas mileage dropped as soon as my temps dropped so I'm fairly certain that it's not getting to temp.